1. Field of the Invention
The present invention relates generally to an apparatus for mixing and dispensing plural component foams, and more particularly, to a dispensing gun for mixing and dispensing a two-component urethane foam utilizing pressurized gas. Preferably, the dispensing gun is a disposable-type gun suitable for use as part of a disposable foam component kit.
2. Description of the Related Art
In recent years, improvements have been made in dispensing plural component synthetic materials, primarily foams, many of which are urethane foams or those involving similar chemistry. In such foams, an “A” or isocyanate component and a “B” or resin component are mixed in a mixing chamber adjacent the point of dispensing and the thus-formed mixture reacts in or near the dispensing nozzle. The combination of the heat from the reaction between the resin and the isocyanate components, and the reduced pressure resulting from passage outside a pressurized container causes a dissolved liquid propellant, such as a halocarbon of low boiling point, to expand and create a froth. Such expansion can also be used to create a propulsive force.
Systems of this sort have been placed in widespread use and have made it possible for a wide variety of users to derive the benefits of on-site generation and dispensing of urethane foam for purposes of insulation, flotation, void fill and the like. Further development enabled urethane foam to be mixed on-site and dispensed from kits that were light enough to be portable by users, and yet large enough to dispense significant quantities of foam. Typically, the kits that are readily portable are capable of mixing and dispensing 100-600 board feet of uniformly high quality urethane foam. Such foam usually has a finished density of 1.5 to 4.5 pounds per cubic foot (“pcf”) and provides buoyancy, adhesion, structural rigidity and outstanding thermal insulation.
When the “A” and “B” components are mixed in proper proportions, they typically react quickly to form and solidify into an expanded foam. Foam dispensing guns must, therefore, be kept free from buildup of the foam components and resulting expanded foam, so that control valves and passageways do not become clogged, rendering the foam dispensing gun inoperable.
U.S. Pat. No. 5,529,245 discloses a low cost mixing and dispensing gun with a valve body containing a pair of liquid inlets, a pair of separate liquid outlets, a gas outlet and a removable mixing and dispensing nozzle. The nozzle contains the ingredients while they are being mixed and a gas outlet is positioned within the nozzle so as to propel the mixed ingredients to the application area.
There is a need for a foam dispensing gun having improved reliability and performance. It is desirable to have a foam dispensing gun with improved component mixing capabilities. It is also desirable to have these improved features in a foam dispensing gun suitable for throw-away use with a disposable portable foam component kit.